Vapor phase cracking apparatus



Dec. 17, 1935. LEvlNE 2,024,828

' VAPOR PHASE CRACKING APPARATUS Filed April 25, 1933 2 Sheets-Sheet l 35 A .56 7 55 I 538 u VAPQRS T0 I A, CRACKED BECRACK 19 q f 27 VAPORS 4% M N/'/ 31 A 1 4g 1 A 4 A i A 10 195A T/IVG GASES IN VEN TOR.

1. Morris Levine. BY 41.4 1/

Dec. 17, 1935.

l. M. LEVINE VAPOR PHASE CRACKING APPARATUS Filed April 25, 1933 2 Sheets-Sheet 2 VAPORS 70 BA; |H

402 C/QA ED VA PORS 50 IN VENTOR.

I. Morris Levine.

Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE VAPOR PHASE CRACKING APPARATUS I. Morris Levine, Fort Worth, Tex., assignor to Texas Pacific Goal & Oil 00., Fort Worth, Tex.,

a corporation of Texas This invention relates to apparatus for the cracking or conversion of hydrocarbons of higher boiling range to produce hydrocarbons of lower boiling range such as gasoline, and more specifically relates to an improved expander for use in vapor phase cracking although it may be useful in other cracking processes.

Many Vapor phase cracking processes include as one step the introduction of vapors at or near a cracking temperature into an expander, from which the cracked vapors are withdrawn to be further processed in any of a number of ways as in a fractionating tower. Such vapors must be heated to a high temperature and due to the fact that they have a relatively low rate of heat transfer, it is essential that they be heated uniformly in such manner as to avoid heating any portions thereof to an excessive degree. In prior constructions, improper functioning of the cracking units have occurred because of the difference between the temperature of the vapors being heated adjacent the wall of the expander and that of the vapor in the center of the expander. Furthermore, mechanical difficulties have been experienced in attempting to make the expander sufficiently flexible to permit expansion and contraction in length and diameter during changes in temperature and at the same time sufficiently air tight that there would be no escape of vapor from the expander. A prior form of expander having a single wall, has in addition to the above objection, a low degree of safety in the event of the occurrence of a leak and consequent combustion of escaping vapors.

It is the principal object of the present invention to provide an expander apparatus in which the vapors to be cracked are uniformly heated and to accomplish the same by constructing an apparatus in which the heating of the vapors in the expander is effected at a plurality of points from within and also at the entire external surface of the expander. This object is attained by constructing a plurality. of spaced heating flues within the expander or vapor chamber and mounting the chamber within a somewhat larger chamber adapted for the passage of heating gases, the heating gases during use of the expander passing in part through the heating fines and in part through the space between the chamber and expander.

Another object of the invention is to provide an improved support for mounting the inner vapor chamber expander in the flue or outer Wall for heating hydrocarbon vapors so that the chamber is free to expand and contract during the great changes in temperature, the vapor connections being located near the support to prevent strains due to the expansion, such vapor connections being readily disconnected for the removal of the vapor chamber from the outer chamber for cleaning or repairing if such becomes necessary.

Another object of the invention is to provide an improved double Walled apparatus for uniformly heating hydrocarbon vapors and liquids which includes an inner vapor chamber having a plurality of equi-distantly spaced tubes for the passage of heating gases and a battle means for the gases passing in contact with the outer walls of the chamber, arranged to proportion properly 15 the heating gases as between the outer surface of the expander and the inner surface of the tubes within, to obtain uniform heating.

Other objects of the invention will appear from the following description thereof taken in connection with the attached drawings which illustrate preferred embodiments of the device and in which:

Figure 1 is a vertical section showing the relative location of an expander and a flue gas cham- 25 ber,

Figure 2 is a similar vertical section showing a slightly modified form of internal construction,

Figure 3 is a plan view of the ring M, of Figure 1, and,

Figure 4 is a plan View of a modified form of ring.

The expander preferably includes two chambers, the larger of which may be termed the heating gas or flue gas chamber IE which is adapted 35 to receive hot gases from any desired source not shown, which gases in preferred practice are introduced through the opening I l, to pass upwardly through the chamber It. Within this chamber the vapor chamber or expander proper 40 I2 is mounted and is heated by the hot gases introduced at the inlet H. The vapor chamber !2 is supported preferably as shown in Figure 1 by means of flange [2a, which may be and preferably is the edge of the top plate of the vapor chamber [2 overlapping the wall I22), supported by an annular perforated ring I4 in turn supported by the flange lilw of the wall of the flue gas chamber l0. Suitable angle brackets i6 attached to the wall of said chamber It! further support the ring 14.

The vapor chamber I 2 is provided with a series of longitudinal heating tubes 11 which are uniformly spaced from each other and from the side walls 12b of the vapor chamber. These tubes 5 are flues for the passage of a portion of the hot gases passed in contact with the vapor chamber. The vapors to be cracked, continually passing through the vapor chamber enter through the inlet conduit l8 which conduit is connected through a suitable stufling box I 9 attached to the outside of the wall of the flue gas chamber Ill. The conduit l8 extends into or is threaded into a fixed union 22 welded or otherwise permanently secured inthe Wall of the vapor chamber. A fixed extension conduit 23 is connected to the union 22 on the inside of the chamber l2 and causes the vapors to pass downwardly to be liberated near the bottom of the vapor chamber. After passing upwardly through said chamber the vapors are discharged through the outlet pipe 21 which pipe is similarly secured toa fixed union 25. The outlet pipe also extends through a stuffing box 26 mounted on the outside-of the flue gas chamber In, the pipe 21 leading the heated vapors to other apparatus for further processing. If desired the vapors may be passed into another expander, although it is usually unnecessary inasmuch as suflicient heat may be acquired for the reaction in one expander.

In view of the arrangement of the heating tubes I! and the provision of external heating of the chamber I2, the flue gases will enter into relatively close indirect contact with all parts of the vapors passing through the chamber, imparting to them a uniform quantity of heat and resulting in a uniform temperature throughout the vapor space in any cross section of the chamber, a result not possible withany indirect heat exchange cracking chambers heretofore known. Baflles 29 may be provided between the respective chambers to regulate the flow of heated flue gases passing upwardly in contact with the exterior of the vapor chamber l 2. The size of the apertures 3| in saidbaffle are dependent upon the size and number of tubes I1 and are so chosen as to proportion the heating gases between the tubes and the annular space between the chambers to obtain a heating of the vapors near the chamber '32 as shown in Figure 3. These apertures may be in the form of elongated arcuate slots, as shown in Figure 3 or as illustrated in the modified ring M11 in Figure 4 they may be in the form of small holes or perforations 34.

After heatingthe chamber 12 the gases pass into the collecting chamber or hood 33 from which they pass out through the discharge conduit 35 to the stack (not shown). The chamber 33 is in the form of a cap or hood which is suitably bolted to the top of the wall of the flue gas chamber In, the bolts 36 projecting through the cap flange 33a, ring I4 and flange lOa. Suitable gaskets, are provided where necessary. The continued use of the expander causes objectionable accumulation of soot, etc., which must be removed. To dismantle the apparatus the cap 33 and the vapor inlet and outlet connections l8 and 21 are detached. The vapor chamber I2 is then removed by merely lifting the same out of the casing, the extended portion of the nipples 22 and 25 slipping through the slots 20 provided in the ring l4. It is to be noted that the vapor inlet and outlet connections have been placed tween the same will be small and stresses and strains will be at a minimum.

This form of construction has many advantages over prior constructions, including simplicity, ease of cleaning and increase in safety. 5 Should any failure occur in the wall of chamber l2 even under circumstances in which there is a large excess of oxygen in the flue gases used for heating the Vapors, resulting in the combustion of the escaping vapors, the fire will be confined to 1 the flue spaces in chamber H] and quickly brought to the notice of the operator by the presence of smoke in the flue gas issuing from the stack.

Another important additional factor of safety obtained by this construction is that ruptures of 15 the inner chamber will not cause the projection of vapors into the atmosphere surrounding the expander apparatus. If, for example, there is a mechanical failure of one or more of the heating tubes, top or bottom plates, or inside wall with a 20 consequent escape of processed oil or vapors, the escaped vapors will be diluted with the flue gases and will pass up the stack. The danger of flashing and combustion of the escaped vapor on the outside of the plant is therefore greatly reduced. 25

Another advantage of the double wall construction becomes apparent in the event of a failure of the outer wall. In the instant construction such failure will involve no danger, for

the gases which will escape are inert combustion V gases. Provided the break is not too large, the same can be repaired without ceasing the operation of the conversion process. If necessary a larger quantity of heating gases may be introduced to make up for that portion lost through the break.

In the preferred construction, the expander or vapor chamber I2 is fabricated from steel or other heat resistant metal or alloy. The outer wall ID of the flue gas chamber may be, however, con- 40 structed either of metal or of any refractory material such as brick, choice being dependent upon the considerations of cost and ease of fabrication.

The particular form of expander hereinbefore described is designed and constructed for the 4,5

treatment of vapors in vapor phase cracking, although the same is satisfactory for the heating of liquid oil in liquid phase cracking and for the heating of fluids partially in vapor form and partially in the liquid state.

A slightly modified form of construction 01 expander is shown in Figure 2 which includes the outer or flue gas chamber wall 40 made of brick, steel or other construction material, having an upper flange 40a supporting a ring I4 or Ma which in turn supports the expander or vapor chamber 42.

In this embodiment the expander 42 has a partition 44 preferably attached to the top 42a of the expander and which extends almost to the bottom thereof. The partition may be positioned in the middle of the expander as designated in the drawings, or to either side of the middle. This partition 44 divides the chamber into two parts, the one on the left indicated at 45 serving as the inlet chamber into which the vapors are introduced through the conduit 46 and the part on the right indicated at 49 serving as the outlet chamber. The vapors introduced into the expander will fill the space between the tubes 41 in the left hand part 45 through which flue gases pass and will become partially heated. Due to the pressure maintained on the vapors, they will travel downwardly in this chamber, pass under the bottom of the partition 44 through the channel 48 into the second chamber 49 through which they will journey in an upward direction and from which they will be discharged through the outlet conduit 50.

As in the first embodiment, flue gases pass between the walls 42 of the vapor chamber and the Wall 40 of the flue gas chamber indicated as the annular passage 52. A proper correlation of the size and number of apertures 34 in the ring I4a at the top of the flue gas chamber controls the amount of gases which pass through this annular passage 52. This ring Ma, may be supplemented by an additional baflle as shown at 29 in Figure 1. The flue gas chamber is surmounted by a cap or hood 54 which is suitably bolted to the frame or flue gas chamber wall 40 in such manner as to maintain the apparatus in a gas tight relation, the flue gases discharging through the outlet 56 to the stack (not shown).

In this construction as in the first embodiment, the inlet and outlet vapor conduits extend through stuffing boxes 60 mounted on the wall 40 and are screwed into fixed unions 59 mounted in the wall 42 of the vapor chamber. In order to allow for expansion, the inlets and outlets are preferably mounted at a point near the point of support of the vapor chamber, between which points there is not much expansion.

The heating of the vapors in this form 01 the apparatus takes place in steps, due to the partition 44. Furthermore the multiplicity of equally spaced tubes and the provision for the heating of the outside wall of the vapor chamber heats all portions of the vapors simultaneously making it possible to use a small differential of temperature between the heating gases and the vapors.

Although termed an expander because of the reaction which takes place, the vapor chamber is a special form of heat exchanger particularly adapted for heating vapors to bring about cracking. A special advantage of the present device resides in that the vapor chamber may be readily removed from the flue gas chamber and cleaned and inspected as desired.

The tubes 41 are secured to the respective headers of the vapor chamber by rolling, welding or other methods adapted to make the vapor chamber pressure tight at all times, in spite of the stresses set up due to the differentials in temperatures to which the expander. is subjected.

Although the particular embodiments illustrated show cylindrical flue gas chambers and vapor chambers, it is to be understood that other shapes may be equally as satisfactory as far as operating conditions are concerned, although for manufacturing reasons the cylindrical type is preferable.

While I have shown and described only two embodiments of my invention I am aware that modifications may be made without departing from the present invention and I therefore desire a broad interpretation of my invention within the spirit and scope of the description herein and of the claims appended hereinafter.

I claim:

1. In an apparatus for cracking hydrocarbon oils in vapor phase, a vertically disposed flue gas chamber for the passage of heating gases, a vertically disposed vapor chamber spaced therefrom, supported within said first chamber and having top and bottom plates and a plurality of tubes extending vertically therebetween, conduits to introduce oil vapors into and conduct them from said vapor chamber, said tubes serving for the passage of heating gases, baffles between the walls of said chambers adapted to diminish the flow of gases, said flues and battles being of such rela- 10 tive size that they are adapted to proportion heating gases between the flues and the passage between the walls, thereby to obtain a substantially uniform temperature throughout the cross section of said vapor chamber. 15

2. An expander tank for cracking hydrocarbon vapors comprising an outer flue gas chamber and an inner vapor chamber, said vapor chamber being adapted for the transmission therethrough and heating therein of hydrocarbon vapors, said 20 vapor chamber having a plurality of hollow conduits extending therethrough for the passage of flue gases therethrough and for the intimate but indirect exchange of heat throughout the vapor chamber, said vapor chamber being spaced from 25 the flue gas chamber wall thereby providing a further passage for flue gases between said vapor chamber and said flue gas chamber, a series of baffle rings in said last mentioned passage to restrict the quantity of flue gas, means to support 30 the inner vapor chamber at one end only, to prevent buckling of said chamber upon expansion thereof, vapor inlet and outlet connections sumciently near the support for the inner vapor chamher to avoid stresses and consequent strains, said 35 inner vapor chamber being removable from said flue gas chamber having a detachable portion permitting removal of said inner vapor chamber.

3. An expander tank for heating hydrocarbon gases consisting of a flue gas chamber, a vapor chamber mounted therein and spaced therefrom, said vapor chamber having a plurality of flue gas passages extending therethrough, means to support said vapor chamber at one end thereof to permit expansion of the same, means to introduce vapors into and discharge the same from said vapor chamber, means to proportion the flow of gases through the space between the chambers and through said flue gas passages, and means permitting easy removal of the vapor chamber from the flue gas chamber.

4. An expander tank for heating hydrocarbons to a cracking temperature which comprises, a chamber, a plurality of vertically extending heating flues extending through the chamber, said flues providing a plurality of internal heating zones, means to heat said zones and the outer wall of said chamber, inlet and outlet means for the continuous passage of said hydrocarbons through said chamber and means within said chamber to cause incoming hydrocarbons introduced near the top thereof to pass to the bottom of said chamber and discharge from the top thereof, said means including a partition extending from the top of said chamber substantially to the bottom thereof.

I. MORRIS LEVINE. 

